Determinants of abnormal maximum oxygen uptake after lung transplantation for chronic obstructive pulmonary disease

Background: Single lung transplantation for chronic obstructive pulmonary d isease relieves a ventilatory limit to incremental exercise, but maximum ox ygen uptake remains abnormal. The purpose of this study was to define the r elative contributions of Pick principle variables to abnormal aerobic capac ity after lung transplantation. Methods: Twelve paired incremental cardiopulmonary exercise test results ob tained before and 3 to 6 months after single lung transplantation for chron ic obstructive pulmonary disease were compared. Results: Maximum workload neatly doubled after operation (42.5 +/- 4.2 vs 2 5.5 +/- 4.7 watts, P <.05). Peak exercise minute ventilation increased (32. 8 +/- 3.3 vs 21 +/- 2.4 L/min, n = 11, P <.05), but maximum oxygen uptake r emained markedly abnormal after transplantation (46.6% +/- 4.4% vs 32.1% +/ - 2.9% predicted, P <.05, n = 8). Peak exercise cardiac output was normal ( 11.0 +/- 1.4 L/min, 89% predicted), but arterial - mixed venous oxygen cont ent difference at peak exercise was only half of normal (7.2 +/- 0.61 mL/dL ), as a result in part of the failure of mixed venous oxygen saturation to fall normally (peak exercise SVO2 = 49.8% +/- 2.8%). Conclusions: Lung transplantation for chronic obstructive pulmonary disease relieves a ventilatory limit to exercise, but maximum aerobic capacity rem ains abnormal, in part because of abnormal systemic O-2 extraction.